Amos e



(ModeL) I v A E DOLBEAR Mode of Transmitting Sound by Electricity.

www/e/ss/ex 9/67M .To all whenvit inlay concerm 'Somerville, in the county of Middlesex and v of which the following-lea full,-clear,

' and'exact description,

purpose.

that one terminal of an open circuit will atiron, the

v transmitter of suitable U preferred being that shown in myapplication fora patent tiled May 31, 1880, the transmitter .T and the battery B being in circuit withe this plate 1 in receiver I and causes it to at-. tract" plate b, which is mounted closet-o, but

not in contact with, plate a,- but as plate 6 in 7 rand adjusting-screw -u. are all of metal.

' the receiver I. The plate b may be made in,

rice in receiver I the plate b and back-piece back-piece r horscrew a of receiver I is con-' MTEE; ST

g Amos E.. noLnnAn, OFSODIERVILLE, mssacirusn'rrs.

' Mens- :OE realism-rims s'ouno ev zLecralcaT ePncrrrcnnou tamin Mamsajm we. aeas'la, datfld A ril 26,1881.

Applloatl on died February 24, 1881.

Be it known that I, AMos- E. DoLBEAn, of

State of Massachusetts, have invented a new mode of Transmitting Sounds by Electricity, concise, reference being had to the accom buying drawings, making a part hereof.

My invention consists, mainly, in a new mode of tiansmitting articulate and other. sounds by an open circuit;

It also consists in new apparatus for this My receiver is based upon the discoveryt-ract and be attracted by a neighboring body' when the terminal is charged.

Fignre'l'shows two modifications of my receiver, insection, connected in circuit with a three pieces, r being the back-piece, s the carceiver I is a thin elastic disk, preferably of vibrations of which reproduce the sound which causes'the diaphragm of the transmitter T to vibrate, T representing a construction, the form the primary coil, as will be clear withoutfun' ther description. l

In receiver Ithe plate a is one terminal of the secondary coil F,{ and any change .in the electrical state of coil F varies the potential of receiver I is so mounted that it cannot vi brate, plate a will vibrate as its potential v.

It will be seen that neither, the plate b nor ncctcd to the coil F, but that only one terminalof coil F-viz., plate g-forrus any part of mom.) I V one piece with back-piece 1'; but for purposes of adjustment is best made as shown.

The force of the attraction between the -charged terminal a and any neighboring body is slight, unless the'neighboring body be many times larger than the terminal and itself capable of being readily electrified, and for this reason, when the neighboring body is a plate,

(as itis best made for purpose of adjustment, .it should .be electrically connected with a larger body. Consequently the back-piece r of the caseof receiver I is made of metal, and is in metallic contact with plate b. The neighboring body, which is attracted by plate a in receiver I, (beingfln fact, the plate b, piece r, and screw a, which are all of metal and in metallic contact,) acts as one body in this receiver I;

- but, as will be clear, the back-piece 1-, plate b, and screw it may be one single piece of metal, and some other provision be made for the necessary adjustment.

In receiver I I the terminal a is mounted upon back-piece 1', so that it cannot vibrate, and must thereforebe insulated. Consequently the -backq1iece r is made of hard rubber. The plate I), which is the neighboring body in re- .ceiver I I, is connected by the wire 'b" with a metal band, 2, upon back piece r, in order'to trification of a greater mass than plate I), and

of plate b, which, in receiver I I, vibrates as the potential of terminal a varies. It will be clcar'that either of the plates b may be grounded, and thereby increase the electrification of these plates; but it is not necessary to ground either of them, and the audibility of the sounds reproduced is practically as great when. the back=piece of the receiver is held in the hand as when the plates 1) are both grounded; and it makes no difference whatever whether both be grounded or only one. In othcrwords, receiver I will reproduce articulate and other sounds, even if back-piece r be of -hard rubber or other non-conductor increase the attractive force due to the elecand. plate I be wholly disconnected from coil F, .butthe sounds reproduced are-faint, although dist-inct and audible. The sounds will be louder if the piece r bc of metal, as above e I I aeoeae band a: and wire b are used, as shown, or'

when plateb of receiver I I is grounded. Mover, the reproduction of sound by receiver I does not depend at all upon the grounding of any part of receiverI I, for receiver I will act with plate b of receiver I I not grounded precisely as it does when plate b ofreceiverI I isgrounded, and receiverI I will act when plate b of receiver 1 isnot grounded precisely as it acts when that plate of receiver I is grounded. In my application filed October 31, 1880, I have described a receiver-in which both the plates a and b are connected with the coil F,

and I therefore disclaim in, this application any receiver having both the plates connecied with that coil, my present invention consisting in a receiver in which only one terminal of the coil is used, as above explained.

Ind of making plate b of metal and conmeeting it metallically with k-piece r or .2 band r, it maybe made of any non-condnctor, and in this the increased loudness is produced by electrifying plate b before it is put in place; or, as shown in receiver I I I,where b is a rubber plate, and b is a disk of felt fast to the hard-rubber support bfiwhich is turned by the thumb and finger to electrify rubber plate b by friction. I 7

What I claim as my invention is- In combination, a primary coil in .eircuit 5 with battery B and transmitter T, and a secondary vcoil with its enlarged terminal a mountedin case r at, and arranged near plate b, plate b being also mounted in case rs t, but not connected with the secondary coil, all-sub; 4o stantially as described.

I Amos E. DOLBEAR.

Witnesses: 1

J; E. MAYNADII'IR, J our: R. Snow. 

